Toxicology
Toxicology is the study of the effects of chemicals on living things. We tend
to think of some chemicals as toxic and others as nontoxic, but in fact, any
chemical is toxic at high enough concentrations.

The food we eat, the water and beverages we drink, and the air we breathe
all are made up of complex mixtures of chemicals. Many of these chemicals are
beneficial to our health when we consume them in small amounts but would be
harmful at larger doses. For example, vitamin D is an important part of the
human diet, but it also is a highly toxic chemical. In tiny amounts it is good
for you, but taking higher than the recommended doses can cause serious health
problems including kidney stones, high blood pressure, deafness, and even death.

Environmental toxicology is the study of the effects
of chemicals on plants, animals, and the ecosystems in which they live. Scientists
use experiments called bioassays
to determine the effects of chemicals on living things.